The academic died "peacefully" at 12:30 (10:30 GMT) at the Life Cycle clinic in Basel, from an infusion of Nembutal, a barbiturate, said Philip Nitschke, founder of Exit International, the group which helped him take his own life.

He was visibly frustrated by the process of formal paperwork, and Mr Nitschke later said: "In fact his last words were 'This is taking an awfully long time!'"

Mr Goodall's last meal was his favourite - fish and chips and cheesecake - and in his final minutes he was played Ode to Joy from Beethoven's 9th symphony.

What was David Goodall known for?

Mr Goodall had lived on his own in a small flat in Perth, Western Australia, until only a few weeks before his trip to Switzerland.

He stepped back from full-time employment in 1979, but remained heavily involved in his field of work.

Media playback is unsupported on your device

Media captionDavid Goodall, 104, sets out his reasons for travelling to Switzerland to voluntarily end his life

Among his achievements in recent years, Mr Goodall edited a 30-volume book series called Ecosystems of the World and was made a Member of the Order of Australia for his scientific work.

In 2016, aged 102, he won a battle to keep working on campus at Perth's Edith Cowan University, where he was an unpaid honorary research associate.

Mr Goodall said he resented having to leave Australia to end his life.

Assisted dying is legal in only one state, but eligibility requires a person to be terminally ill. The Australian Medical Association (AMA) is strongly opposed to assisted dying, which it sees as an unethical practice of medicine.

Meanwhile, Switzerland has allowed assisted suicide since 1942.

Mr Goodall arrived in Basel on Monday after visiting relatives in France, and spent his final full day exploring the Basel University botanic gardens with three of his grandchildren.

At a press conference on Wednesday, he said he was surprised by the public interest in his case. He added: "I no longer want to continue life.

"One wants to, at my age, even rather less than my age... to be free to choose death when the death is at an appropriate time."

He wanted no funeral and requested that his body be donated to medicine or his ashes sprinkled locally, Exit International said.

Where else is assisted dying allowed?

Assisted suicide describes any act that intentionally helps another person kill themselves, for example by providing them with the means to do so, most commonly by prescribing a lethal medication.

It differs from euthanasia, which is a third-party intervention to end a life to relieve suffering, such as when a doctor administers the lethal dose.

In Switzerland, assisted suicide is allowed only if the person assisting acts unselfishly. It is the only country with centres offering assisted suicide to foreign nationals

The Netherlands, Belgium and Luxembourg permit euthanasia and assisted suicide. In the Netherlands and Belgium, euthanasia is available to minors in specific instances

Colombia allows euthanasia

The US states of Oregon, Washington, Vermont, Montana, California, Colorado and Hawaii permit assisted dying for terminally ill patients. The US capital Washington DC implemented a similar law for the city's residents in 2017

Canada followed the province of Quebec in permitting euthanasia and assisted suicide in 2016